Climate change has increased the incidence of coral bleaching events, resulting in the loss of ecosystem function and biodiversity on reefs around the world. As reef degradation accelerates, the need for innovative restoration tools has become acute. Despite past successes with ultra-low temperature storage of coral sperm to conserve genetic diversity, cryopreservation of larvae has remained elusive due to their large volume, membrane complexity, and sensitivity to chilling injury. Here we show for the first time that coral larvae can survive cryopreservation and resume swimming after warming. Vitrification in a 3.5 M cryoprotectant solution (10% v/v propylene glycol, 5% v/v dimethyl sulfoxide, and 1 M trehalose in phosphate buffered saline) followed by warming at a rate of approximately 4,500,000 °C/min with an infrared laser resulted in up to 43% survival of Fungia scutaria larvae on day 2 post-fertilization. Surviving larvae swam and continued to develop for at least 12 hours after laser-warming. This technology will enable biobanking of coral larvae to secure biodiversity, and, if managed in a high-throughput manner where millions of larvae in a species are frozen at one time, could become an invaluable research and conservation tool to help restore and diversify wild reef habitats.
Bibliographical noteFunding Information:
This research was supported by funds from the Smithsonian Conservation Biology Institute, the Hawaii Institute of Marine Biology, the Paul M. Angell Family Foundation, the Roddenberry Foundation, the Seaver Institute, the William H. Donner Foundation, the Barrett Family Foundation, the Skippy Frank Foundation, the Compton Foundation, the Cedar Hill Foundation, and the Anela Kolohe Foundation. J.D. was supported by a Paul M. Angell Family Foundation fellowship. J.B. was supported by funds from the National Institutes of Health (NIH R41 OD024430-01) and the Carl and Janet Kuhrmeyer Chair in Mechanical Engineering. We would like to thank Rita Steyn for assistance with histology, Amy Eggers and the Gates Coral Lab for assistance with confocal imaging, Gin Carter and Eneour Puill-Stephan for technical assistance, and David E. Wildt for manuscript review. Collection of coral was conducted under Special Activity Permit Number SAP 2018-03 issued by the State of Hawaii Department of Land and Natural Resources.